This paper is an effort to build on the essays collected in our three NBER conference volumes by offering a new synthesis of American business history. We move beyond the traditional markets versus hierarchies (or markets versus central planning) dichotomy and argue that one can observe in the cross-section of the economy at any moment in time a variety of coordination mechanisms in use, man of which do not fit neatly into these ideal types. We argue further that one can speak of the incidence of these different mechanisms in cross-section, and hence one can speak of modal mechanisms and hence of the history (that is, evolution) of these cross-sections. Finally, we argue that changes over time in the incidence of these coordination mechanisms were propelled by forces that can be taken as exogenous including, most importantly, improvements in transportation and communications, urbanization, and the general rise in per capita income.